PKM2 dictates the poised chromatin state of PFKFB3 promoter to enhance breast cancer progression

Abstract

The hypoxic milieu is a critical modulator of aerobic glycolysis, yet the regulatory mechanisms between the key glycolytic enzymes in hypoxic cancer cells are largely unchartered. In particular, the M2 isoform of pyruvate kinase (PKM2), the rate-limiting enzyme of glycolysis, is known to confer adaptive advantages under hypoxia. Herein, we report that non-canonical PKM2 mediates HIF-1α and p300 enrichment at PFKFB3 hypoxia-responsive elements (HREs), causing its upregulation. Consequently, the absence of PKM2 activates an opportunistic occupancy of HIF-2α, along with acquisition of a poised state by PFKFB3 HREs-associated chromatin. This poised nature restricts HIF-2α from inducing PFKFB3 while permitting the maintenance of its basal-level expression by harboring multiple histone modifications. In addition, the clinical relevance of the study has been investigated by demonstrating that Shikonin blocks the nuclear translocation of PKM2 to suppress PFKFB3 expression. Furthermore, TNBC patient-derived organoids and MCF7 cells-derived xenograft tumors in mice exhibited substantial growth inhibition upon shikonin treatment, highlighting the vitality of targeting PKM2. Conclusively, this work provides novel insights into the contributions of PKM2 in modulating hypoxic transcriptome and a previously unreported poised epigenetic strategy exhibited by the hypoxic breast cancer cells for ensuring the maintenance of PFKFB3 expression.

Oncometabolite lactate enhances breast cancer progression by orchestrating histone lactylation-dependent c-Myc expression

“…The culture media for all the cell lines was supplemented with 10% fetal bovine serum (FBS; Sigma, F7524), 100 units/ml of penicillin and streptomycin (Invitrogen, 15140122), and 2 mM/ l -glutamine (Invitrogen, 25030081). The Boris Binding Site mutant (BBS Mut) MCF7 and HCC1806 cell lines were generated as previously stated [ 30 , 31 ]. The media and cell culture conditions for CRISPR/Cas9 mutants were identical to the wild-type cells.…”

“…The PKM2 and PFKFB3 overexpression constructs were generated as previously mentioned [ 30 , 31 ]. Briefly, PKM2 was amplified using MCF7 cDNA as a template and cloned between Not I and Sal I sites of the plasmid pCMV-3tag-1a.…”

“…The ChIP assay was performed as previously mentioned [31] . Approximately 10 million cells were crosslinked, scaped in PBS, lysed, and sonicated.…”

Non-metabolic enzyme function of PKM2 in hepatocellular carcinoma: A review

“…[ 14 ] Interestingly, studies have also demonstrated that PKM2 can regulate HIF-1α expression and activation. [ 12 , 15 – 17 ] Azoitei N et al [ 12 ] found that PKM2 entered the nucleus and activated NF-κB/p65 and HIF-1α in hypoxic pancreatic tumors, leading to increased transcription of vascular endothelial growth factors, ultimately triggering vascular endothelial growth factors-A secretion and angiogenesis. Liu WR et al [ 15 ] found that knocking down PKM2 in highly metastatic liver cancer cells HCCLM3 could reduce the expression of HIF-1α protein and the phosphorylation of AKT and JUK, while reducing liver cancer cell angiogenesis ability, reducing the number of tubules, number of tubules branching points, and tubule length.…”

“…Furthermore, recent research reported that the recruitment of HIF-1α and p300 mediated by nuclear PKM2 under hypoxia in breast cancer cells also caused the upregulation of 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 3 a glycolytic enzyme and positively associated with cancer progression and aggression). [ 17 ] These studies suggest that nuclear PKM2 can promote glycolysis by activating HIF-1α, potentially playing a role in various biological functions of HCC. These findings highlight the potential of PKM2/HIF-1α as a target for anti-HCC therapies.…”